Monostatic antennas are typically used in radar systems relevant here in the field of automobile technology, in which a shared antenna lens is used for emitted and received signals (TX/RX feeds). The polarization axes, i.e., the axes of the associated electrical field vectors of these two signals, usually have an angle of 45° in the cited radar systems, in order to ensure that the signals originating from an oncoming vehicle equipped with an identical radar are received cross-polarized in relation to the received signal of the host vehicle. Because of this measure, disturbing interference between the signals of the two vehicles is effectively suppressed.
Until now, usually only long-range radar (LRR) systems have been used in the field of automobile technology for long-range detection. However, there is increasing demand in automobile technology for the use of short-range radar (SRR) systems using short-range detection, for example, for performing distance measurements in bumper-to-bumper traffic or for use as a parking aid.
The detection field for short-range applications generally has a significantly larger beam angle in comparison to long-range applications. However, because of the smaller EIRP (equivalent isotropic radiated power) value in the short-range applications, these also have a shorter range. The cited EIRP represents a pure operand and indicates what transmission power an antenna emitting uniformly (isotropically) in all spatial directions must be supplied with in order to achieve the same power flux density in the far field as with a bundling directional antenna in its main transmission direction.
For these reasons, it is not possible to provide the same antenna aperture for the LRR and SRR functions.